Biological assays that require sample partitioning are traditionally performed in test-tubes or microwell arrays and require manual intervention at several stages to enable the sampling, purification, reagent addition, and detection steps required to make the assay selective and specific. Ongoing developments in this field have focused on the ability to rapidly process fluid samples in order to increase efficiency and cost effectiveness. In some cases, automated sample handling equipment has been developed to reduce the amount of manual intervention and to assist in the detection of assay reaction products in multiple microwells of an array, thereby increasing the speed and efficiency of fluid sample testing, handling and preparation. However, because of the bulk of the automated equipment, these tests are often difficult to perform in the field.
In addition to these developments, there has been a drive towards reduction in size of the instrumentation used for analysis and manipulation of the samples. This reduction in size offers several advantages in addition to increased analytical speed, such as the ability to analyze very small samples, the ability to use reduced amount of reagents and a reduction in overall cost.
An outgrowth of these size reductions is an increased need for accuracy in the quantity of fluid sample provided. With volumes in the micro-liter range, even miniscule variations in sample quantity may have a significant impact on the analysis and results of the fluid sample tests. As a result, articles used to house the fluid samples during preparation, handling, testing and analysis are required that provide extremely accurate fluid containment and fluid transport structures on or in the articles. Highly accurate articles for microfluid handling and analysis have been produced from glass or silicon substrates having lithographically patterned and etched surface features. Using lithographically patterned glass or silicon based microfluidic chips, fundamental feasibility has been established for microfluidic chip based enzyme assays, immunoassays, DNA hybridization assays, particle manipulations, cell analysis and molecular separations. However, there remains a need in the art to combine these various functions to support complex biological assay tasks important to biomedical R&D, pharmaceutical drug discovery, medical diagnostics, food and agricultural microbiology, military and forensic analysis. Glass and silicon based chips pose several practical problems to reaching these objectives. These problems relate to the high cost of manufacture, incompatibilities between discrete processes for microfabrication of the glass substrates and continuous processes for incorporating the assay reagents, and the difficulties associated with sealing a glass cover onto the reagent impregnated chip. Articles formed from plastic substrates, such as polyimides, polyesters and polycarbonates, have been proposed as well.
Size reductions in the field have also produced a need for devices and methods for introducing fluid sample into the highly accurate fluid containment and transport structures. Some current methods include dispensing of the fluid sample via one or more pipettes, syringes, or other similar devices. This mechanical introduction of a fluid sample requires accurate alignment between the fluid dispensing device and the test device, as well as accurate metering of the amount of fluid sample dispensed.
In order to accommodate the need for high throughput analysis systems (both automated and manual), substrates provided with a plurality of fluid sample handling and analysis articles have been developed. Such substrates may be formed as flexible rolled goods that allow simultaneous and/or synchronous testing of fluid samples contained in the plurality of articles. Alternatively, such substrates may be formed as rigid, semi-rigid or flexible sheet goods which also may allow for simultaneous and/or synchronous testing of the fluid samples housed therein. Optionally, articles may be detached from the roll or sheet provided goods to accommodate limited testing.
There is an ongoing need for efficient, cost effective and rapid testing of fluid samples, especially in the area of biological detection assays as described above, coupled with a requirement for accuracy in fluid quantities and article structures. This combination has produced a corresponding need for manufacturing and formation methods which produce the required fluid testing articles in a cost effective and efficient manner while maintaining accuracy within a particular article, and from article to article. In addition, an ongoing requirement exists for fluid testing article designs that meet the various fluid handling, testing and analyzing needs of the diagnostic, forensic, pharmaceutical and other biological analysis industries, which adhere to the strict requirements of efficiency, cost effectiveness and accuracy described above while also simplifying the testing and analysis processes. Furthermore, it would be advantageous to provide a fluid handling architecture that partitions a sample into aliquots, each aliquot to be reacted with a different combination of assay reagents. It would also be advantageous to provide a fluid handling architecture with additional optical or electronic features that enhance the detection of fluorogenic or chromogenic indicators, electrochemical reagents, agglutination reagents and the like.